A PUMP

Description

[0001] The invention relates to a pump particularly, but not exclusively, to a diaphragm pump suitable for pumping liquids.

[0002] Diaphragm pumps have been in use in industry for some years. In such pumps, diaphragms or cylinders are caused to move in a reciprocating manner within a chamber and sealing means are provided between the interior wall of the chamber and the moving diaphragm or cylinder. Sealed portions of the chamber are thereby created between the ends of the chamber and the relevant face of the appropriate diaphragm or cylinder. Any movement of the diaphragm or cylinder within the chamber therefore causes the pressure within that sealed portion of the chamber to change. Commonly, venting means are provided to allow the pressure within that portion of the chamber to return to ambient pressure at appropriate intervals during the operating cycle.

[0003] In certain instances, this venting can cause problems. For example, pumps of this type can be designed to transport liquids having internal pressures in the order of 1,24-1,93 bar (18-28psi) created by internal carbonisation. Carbon dioxide or other gas or gas mixture supplied at a pressure of, for example, 4,14 bar (60psi), is introduced into the relevant portion of the chamber in order to move the appropriate diaphragm or cylinder from one operating position to another. When the reciprocal motion is to take place, the carbon dioxide or other gas at 4,14 bar (60psi) is vented to atmosphere. This causes a pressure differential across the sealing means located between the diaphragm or cylinder and the interior wall of the chamber. Repeated pressure differences of this type can cause deterioration of the sealing means which must then be regularly inspected and, if necessary, replaced.

[0004] It is an object of the invention to provide a pump which does not have the aforementioned disadvantage and which therefore has an extended working life and reduced maintenance costs. Known diaphragm pumps are shown and described in each of FR-A-2315019 and EP-A-172367. The French document shows a pump having features which prevent the diaphragm coming into contact with its supports in the event of a sudden, unpredictable pressure increase in the fluid being pumped. This does not address the problem of maintaining small pressure differences across the diaphragm during normal operation. The European document discloses stepped venting through a low pressure chamber in order to avoid icing or stalling of the valve. The pressure to which the chamber is vented is not addressed.

[0005] The invention provides a pump as set out in claim 1 of the appended claims. The invention also provides a pumping system as set out in claim 8 of the appended claims and a method of pumping a liquid as set out in claim 10 of the appended claims. Preferred features of the various aspects of the invention are set out in the subsidiary claims.

[0006] Embodiments of a pump according to the invention will now be described with reference to the accompanying drawings wherein:

Figure 1 is a schematic cross-section taken through the longitudinal axis of a pump according to a first embodiment of the invention in a first operation position;

Figure 2 is a schematic cross-sectional view of the pump of Figure 1 shown in a second operating position; and

Figure 3 is an enlarged cross sectional detail of part of a pump according to a second embodiment of the invention.

[0007] The pump shown in Figures 1 and 2 consists of a housing 10 which incorporates an elongate chamber 12 and a transverse through chamber 14 for the passage of pumped liquid. The through chamber 14 has an inlet 16 and an outlet 18, between which are two parallel channels 20,22 which can be opened and closed by means of valves 24a,24b,24c and 24d. The channels 20,22 are variable in volume in their central sections by means of the movement of cylinders 26,.28 which are rigidly connected by connecting member 30. Seals 32a and 32b form liquid-tight connections between the cylinders 26,28 and the interior wall of the chamber 12.

[0008] Cylinders 26 and 28 are arranged so as to be reciprocatingly movable within the chamber 12. The movement takes place along the longitudinal axis of chamber 12 and is controlled by means not shown in detail in the accompanying drawings. Furthermore, gas introduction means 34 are provided to allow the introduction of compressed gas into the chamber either to the left of cylinder 26 or to the right of cylinder 28 as desired. Venting means 36 allowing venting of these portions of the cylinder 12 are also provided.

[0009] The apparatus described thus far is known. However, the venting means 36 are attached to pressure regulating means in the form of a pressure valve 40. The pressure valve 40 incorporates control means and/or sensing means designed to detect the pressure of the liquid within the channels 20,22 or at the inlet 16 and to allow the portions of the chamber 12 to the left of cylinder 26 and to the right of cylinder 28 from being vented to a pressure substantially different from the pressure in the channels 20,22. This prevents undue pressure differences occurring across the seals 32a,32b.

[0010] The operation of the pump shown in Figures 1 and 2 will now be described. In the position shown in Figure 1, cylinders 26,28 have just completed a stroke from right to left. Valve 24a is closed and valve 24b is open having just allowed the liquid to be pumped to enter channel 20 from the inlet 16. Valve 24c is open and valve 24d is closed and the movement of cylinder 28 from right to left has just forced the majority of the fluid in the channel 22 through valve 24c to outlet 18. The pressure in channels 20,22 corresponds to the internal pressure of the liquid being pumped, eg. 1,24-1,93 bar (18-28psi). The pressure in the portion of the chamber 12 to the right of cylinder 28 is approximately 4,14 bar (60psi), this being the pressure of CO₂ or other suitable gas used to move the cylinders 26,28 from right to left. The pressure in the chamber to the left of cylinder 26 is substantially lower to allow the movement to have taken place.

[0011] At the completion of the stroke described above, each of the valves 24a,24b,24c,24d alters its position. Valve 24a opens, valve 24b closes, valve 24c closes and valve 24d opens. Compressed CO₂ or other suitable gas at a pressure of around 4,14 bar (60psi) is introduced into the chamber to the left of cylinder 26 and a return stroke from left to right of cylinders 26 and 28 is initiated. However, instead of the portion of the chamber 12 to the right of cylinder 28 being vented to atmospheric pressure, the pressure regulator 40 comes into operation and allows that portion of the chamber to be vented only to a pressure of substantially the same as that pressure exerted on the seal 32b by the fluid in the channel 22. This means that the pressure difference across the seal 32b is relatively small. Damage to the seal and/or distortion of the seal 32b is thereby minimised.

[0012] When the portion of the chamber 12 to the right of cylinder 28 has been vented to a suitable level, cylinders 26, 28 will move from left to right to the position shown in Figure 2. Because of the position of the seals 24a,24b, fluid previously contained in the channel 20 will be forced through the outlet 18 by the movement of the cylinder 26. Similarly, because of the position of valves 24c,24d, fluid will be drawn into channel 22 by the movement of the cylinder 28.

[0013] At the completion of this stroke, the position of each valve again reverses and compressed carbon dioxide or other suitable gas is then introduced into the chamber 12 to the right of the cylinder 28 via the compressed gas supply means 34. The chamber 12 to the left of cylinder 26 will be vented through the venting means 36 but, as before, the extent of the venting will be regulated by the pressure regulator 40. Again, the pressure difference across the seal 32a will be minimised.

[0014] The reduction of the pressure difference across the seals 32a,32b means that any damage to or distortion of the seals is kept to a minimum. The working life of the seals is thereby increased and maintenance costs relating to the pump are minimised.

[0015] The pressure regulator 40 can take any suitable form. It can be arranged to be preset in accordance with the known internal pressure of a fluid to be pumped by the pump. Alternatively, the pump can be provided with pressure sensors (not shown) inside the channels 20,22 or in the vicinity of the inlet 16 or outlet 18 to detect the internal pressure of the pumped fluid. In this way, the pressure to which the relevant portion of the chamber 12 is vented can be regulated in accordance with the internal pressure of the pumped fluid.

[0016] However, Figure 3 illustrates a regulator 50 which forms part of a preferred embodiment of a pump according to the invention. The regulator 50 would replace the regulator 40 shown in Figures 1 and 2 and can be used in conjunction with a pump having all of the remaining features of the pump shown in Figures 1 and 2. The regulator 50 comprises an upper portion 52 which can be arranged to be connected to the inlet 16 of the pump. If desired, the upper portion 52 can be formed integrally with the inlet 16 or can be connected thereto by suitable connecting means (not shown). The upper portion 52 includes a fluid inlet 54 which is intended to be connected to a supply or reservoir of fluid to be pumped by the pump. The regulator 50 also comprises a lower portion 56 which includes an exhaust gas inlet 58 and an exhaust gas outlet 60.

[0017] Between the upper and lower portions 52, 56 is located a movable shut-off valve 62 comprising a central pin 64 and a flexible diaphragm 66. The diaphragm 66 is fixedly connected to the wall of the regulator 50 and to the central pin 64. The central pin 64 extends downwardly from the diaphragm 66 towards the exhaust gas outlet 60 and, in the position shown in Figure 3, the end of the central pin 64 rests in the entrance to the exhaust gas outlet 60. An O-ring seal 68 is provided between the central pin 64 and the entrance to the exhaust gas outlet 60 such that, when the end of the pin 64 rests in the outlet 60, a gastight seal is produced. However, when an upward force is exerted on the shut-off valve 62, the valve 62 can move upwardly so that the central pin 64 moves out of engagement with the entrance to the exhaust gas outlet 60 and thus the gastight seal provided by the O-ring seal 68 is broken. Any upward movement of the shut-off valve 62 is limited by the diaphragm 66.

[0018] The operation of the regulator 50 is as follows. Fluid to be pumped by the pump is introduced to the inlet 16 via the upper portion 52. Specifically, the supply or reservoir of fluid to be pumped is connected to the fluid inlet 54. The fluid then fills the upper portion 52 of the regulator 50 above the shut-off valve 62. The internal pressure of the fluid to be pumped is therefore exerted on all of the internal surfaces of the upper portion 52, including the upper surface of the diaphragm 66 and the central pin 64. The venting means 36 (see Figures 1 and 2) are connected directly to the exhaust gas inlet 58 by means of a pipe 70. Gas which is vented or exhausted from the portion of the chamber 12 either to the left of cylinder 26 or to the right of cylinder 28 is thus passed directly to the lower portion 56 of the regulator 50. The pressure of the vented gas is therefore exerted on all of the internal surfaces of the lower portion 56, including the lower surface of the diaphragm 66 and the central pin 64.

[0019] When the pressure of the vented gas in the lower portion 56 exceeds the internal pressure of the fluid to be pumped, the shut-off valve 62 is raised thus opening the entrance to the exhaust gas outlet 60. The exhaust or vented gas thus has a free passage out of the regulator 50 via the outlet 60. If, however, the pressure of the exhaust gas drops below the internal pressure of the fluid to be pumped, the shut-off valve 62 will drop to the position shown in Figure 3, ie. with the lower end of the central pin 64 in engagement with the entrance to the exhaust gas outlet 60. The outlet 60 is thereby sealed thus preventing any further escape of vented gas. Only when the pressure of the exhaust gas again exceeds the internal pressure of the fluid to be pumped will the outlet 60 be re-opened to allow the exhaust gas to escape. The exhaust gas is thereby maintained substantially at the internal pressure of the fluid to be pumped.

[0020] It will be appreciated that, if desired, biasing means can be incorporated into the regulator 50 so as to bias the shut-off valve 62 in one direction or another. The effect of this would be to maintain the pressure of the exhaust gas a little above or below the internal pressure of the fluid to be pumped depending upon whether the biasing were downward or upward.

[0021] It is envisaged that a pump of the type indicated above can be included in a pumping system suitable for use in any situation such as, eg. a brewery or public house or any other industrial situation. When the system is intended for use in pumping beverages, the pump will be designed to handle liquids having internal pressures of between 0,48 and 2,07 bar (7 and 30 psi) although liquids having higher internal pressures can preferably be handled. The pumping system will incorporate known means for connecting the inlet 16 of the pump to a reservoir of a liquid, eg. beer or other beverage, and the outlet 18 of the pump will be connected to a conventional dispenser. It is envisaged that a pumping system of this type could incorporate a plurality of pumps as described above and these pumps could be connected to individual dispensers if desired. If a plurality of pumps is provided, they could be supplied by a single reservoir or from separate reservoirs of liquid.

[0022] It will be appreciated that the invention is not limited to the embodiments described above but encompasses any and all variations which will be apparent to a reader skilled in the art.

Claims

1. A pump comprising at least one diaphragm or cylinder (26, 28) movable by means of a working fluid in a reciprocating manner within a chamber (12), sealing means (32a, 32b) located between the diaphragm or cylinder (26, 28) and the interior wall of the chamber (12), and venting means (36) for venting a portion of the chamber (12) bounded by the interior wall, the diaphragm or cylinder (26, 28) and the sealing means (32a, 32b), characterised in that the venting means (36) incorporate pressure regulating means (40) such that the pressure to which the said portion of the chamber (12) is vented can be regulated such that, in use, the pressure of the working fluid in the said portion of the chamber (12) is prevented from falling during venting, below the pressure of a fluid being pumped by the pump.

2. A pump as claimed in claim 1, wherein the pressure regulating means (40) comprise sensors for sensing the pressure of the fluid being pumped by the pump and means for controlling the regulated pressure in accordance with the pressure sensed by the sensors.

3. A pump as claimed in claim 1, wherein the regulating means comprise a movable shut-off valve (62) responsive in use to the difference between the pressure within the said portion of the chamber and the pressure of a fluid being pumped by the pump.

4. A pump as claimed in claim 3, wherein the movable shut-off valve (62) is movable between an open position allowing venting of the said portion of the chamber and a closed position preventing venting of the said portion of the chamber, the valve being moved from the open position to the closed position when, in use, the pressure in the said portion of the chamber drops below the pressure of the fluid being pumped by the pump.

5. A pump as claimed in claim 3 or 4, wherein the movable shut-off valve (62) comprises a further diaphragm (66) exposed, in use, on one side to the fluid being pumped by the pump and on the other side to the vented contents of the said portion of the chamber.

6. A pump as claimed in any one of claims 1 to 5, wherein two diaphragms or cylinders (26, 28) are located in the chamber.

7. A pump as claimed in any one of the preceding claims, wherein the sealing means (32a, 32b) comprise at least one rolling diaphragm seal.

8. A pumping system for pumping a liquid from a reservoir to a dispensing point, comprising a reservoir or attachment means for connection to a reservoir, at least one dispensing point and at least one pump according to any one of claims 1 to 7.

9. A pumping system as claimed in claim 8, wherein a plurality of dispensing points are provided and a separate pump is associated with each dispensing point.

10. A method of pumping a liquid using a pump according to any one of claims 1 to 7, comprising the steps of causing the or each diaphragm or cylinder (26, 28) to move within the chamber (12) and venting the portion of the chamber bounded by the interior wall of the chamber, the diaphragm or cylinder (26, 28) and the sealing means (32a, 32b), wherein the venting of the said portion of the chamber is regulated so as to maintain the pressure in the said portion substantially at the pressure of the fluid being pumped by the pump.

11. A method as claimed in claim 10, wherein carbon dioxide gas is used to cause reciprocating movement of the or each diaphragm or cylinder within the chamber.

Ansprüche

1. Pumpe mit mindestens einer Membran oder einem Zylinder (26, 28), die mittels eines Arbeitsfluids in hin- und hergehender Weise innerhalb einer Kammer (12) beweglich sind, Dichtungsmitteln (32a, 32b), die zwischen der Membran oder dem Zylinder (26, 28) und der inneren Wand der Kammer (12) angeordnet sind, und Ventiliermitteln (36) zum Ventilieren eines durch die innere Wand, die Membran oder den Zylinder (26, 28) und die Dichtungsmittel (32a, 32b) begrenzten Bereichs der Kammer (12), dadurch gekennzeichnet, daß die Ventiliermittel (36) Druckregelmittel (40) enthalten, so daß der Druck, bis auf den der Bereich der Kammer (12) ventiliert wird, so geregelt werden kann, daß während des Betriebs verhindert wird, daß der Druck des Arbeitsfluids in dem Bereich der Kammer (12) während der Ventilation bis unter den Druck eines von der Pumpe gepumpten Fluids absinkt.

2. Pumpe gemäß Anspruch 1, wobei die Druckregelmittel (40) Fühler aufweisen, um den Druck des von der Pumpe gepumpten Fluids zu fühlen, und Mittel aufweisen, um den geregelten Druck entsprechend dem von den Fühlern gefühlten Druck zu steuern.

3. Pumpe gemäß Anspruch 1, wobei die Regelmittel ein bewegliches Absperrventil (62) aufweisen, das während des Betriebs auf die Differenz zwischen dem Druck innerhalb des Bereichs der Kammer und dem Druck eines von der Pumpe gepumpten Fluids anspricht.

4. Pumpe gemäß Anspruch 3, wobei das bewegliche Absperrventil (62) beweglich ist zwischen einer offenen Position, die eine Ventilation des Bereichs der Kammer ermöglicht, und einer geschlossenen Position, die eine Ventilation des Bereichs der Kammer verhindert, wobei das Ventil von der offenen Position in die geschlossene Position bewegt wird, wenn während des Betriebs der Druck in dem Bereich der Kammer bis unter den Druck des von der Pumpe gepumpten Fluids absinkt.

5. Pumpe gemäß Anspruch 3 oder 4, wobei das bewegliche Absperrventil (62) eine weitere Membran (66) aufweist, die während des Betriebs auf einer Seite dem von der Pumpe gepumpten Fluid, und auf der anderen Seite dem ventilierten Inhalt des Bereichs der Kammer ausgesetzt ist.

6. Pumpe gemäß irgendeinem der Ansprüche 1 bis 5, wobei zwei Membranen oder Zylinder (26, 28) in der Kammer angeordnet sind.

7. Pumpe gemäß irgendeinem der vorhergehenden Ansprüche, wobei die Dichtungsmittel (32a, 32b) mindestens eine Rollmembrandichtung aufweisen.

8. Pumpsystem zum Pumpen einer Flüssigkeit von einem Vorratsbehälter nach einer Ausgabestelle, mit einem Vorratsbehälter oder Befestigungsmitteln zur Verbindung mit einem Vorratsbehälter, mindestens einer Ausgabestelle und mindestens einer Pumpe gemäß irgendeinem der Ansprüche 1 bis 7.

9. Pumpsystem gemäß Anspruch 8, wobei eine Vielzahl von Ausgabestellen vorgesehen ist, und jeder Ausgabestelle eine getrennte Pumpe zugeordnet ist.

10. Verfahren zum Pumpen einer Flüssigkeit mittels einer Pumpe gemäß irgendeinem der Ansprüche 1 bis 7, das die Schritte aufweist, bei denen die oder jede Membran oder der oder jeder Zylinder (26, 28) innerhalb der Kammer (12) bewegt wird, und der von der inneren Wand der Kammer, der Membran oder dem Zylinder (26, 28) und den Dichtungsmitteln (32a, 32b) begrenzte Bereich der Kammer ventiliert wird, wobei die Ventilation des Bereichs der Kammer so geregelt wird, daß der Druck in dem Bereich im wesentlichen auf dem Druck des von der Pumpe gepumpten Fluids gehalten wird.

11. Verfahren gemäß Anspruch 10, wobei Kohlendioxidgas verwendet wird, um die Hin- und Herbewegung der oder jeder Membran oder des oder jedes Zylinders innerhalb der Kammer hervorzurufen.

Revendications

1. Pompe comprenant au moins un diaphragme ou un cylindre (26, 28) pouvant être animé, sous l'effet d'un fluide moteur, d'un mouvement alternatif dans une chambre (12), un dispositif d'étanchéité (32a, 32b) situé entre le diaphragme ou le cylindre (26, 28) et la paroi interne de la chambre (12), et un système de purge (36) pour évacuer une partie de la chambre (12) limitée par la paroi interne, le diaphragme ou le cylindre (26, 28) et le dispositif d'étanchéité (32a, 32b), caractérisée en ce que le système de purge (36) incorpore un moyen de régulateur de pression (40) qui sert à réguler la pression à laquelle ladite partie de la chambre (12) est purgée, de manière à ce que, lors de l'utilisation, la pression du fluide moteur dans ladite partie de la chambre (12) n'ait pas la possibilité de chuter, pendant la purge, au dessous de la pression d'un fluide qui est pompé par la pompe.

2. Pompe selon la revendication 1, dans laquelle le moyen de régulateur de pression (40) comprend des capteurs pour détecter la pression du fluide qui est pompé par la pompe et un moyen pour commander la pression régulée de manière correspondante à la pression détectée par les capteurs.

3. Pompe selon la revendication 1, dans laquelle le régulateur comprend une soupape d'arrêt mobile (62) sensible, lors de l'utilisation, à la différence existant entre la pression dans ladite partie de la chambre et la pression d'un fluide qui est pompé par la pompe.

4. Pompe selon la revendication 3, dans laquelle la soupape d'arrêt mobile (62) est mobile entre une position ouverte qui permet la purge de ladite partie de la chambre et une position fermée qui empêche la purge de ladite partie de la chambre, la soupape passant de la position ouverte à la position fermée lorsque, pendant l'utilisation, la pression dans ladite partie de la chambre chute en dessous de la pression du fluide qui est pompé par la pompe.

5. Pompe selon la revendication 3 ou 4, dans laquelle la soupape d'arrêt mobile (62) comprend un autre diaphragme (66) dont un côté est exposé, lors de l'utilisation, au fluide qui est pompé par la pompe et l'autre côté est exposé au contenu évacué de ladite partie de la chambre.

6. Pompe selon l'une quelconque des revendications 1 à 5, dans laquelle deux diaphragmes ou cylindres (26, 28) sont situés dans la chambre.

7. Pompe selon l'une quelconque des revendications précédentes, dans laquelle le dispositif d'étanchéité (32a, 32b) comprend au moins un diaphragme roulant d'étanchéité.

8. Système de pompage servant à pomper un liquide venant d'un réservoir pour l'amener à un point de distribution, comprenant un réservoir ou un moyen de fixation pour la connexion à un réservoir, au moins un point de distribution et au moins une pompe selon l'une quelconque des revendications 1 à 7.

9. Système de pompage selon la revendication 8, dans lequel une pluralité de points de distribution est prévue et une pompe séparée est associée à chaque point de distribution.

10. Procédé pour pomper un liquide en utilisant une pompe selon l'une quelconque des revendications 1 à 7, comprenant les étapes qui consistent à amener le ou chaque diaphragme ou cylindre (26, 28) à se déplacer dans la chambre (12) et à purger la partie de la chambre limitée par la paroi interne de la chambre, le diaphragme ou le cylindre (26, 28) et le dispositif d'étanchéité (32a, 32b), dans lequel la purge de ladite partie de la chambre est régulée de manière à maintenir la pression dans ladite partie sensiblement au niveau de la pression du fluide qui est pompé par la pompe.

11. Procédé selon la revendication 10, dans lequel on utilise du dioxyde de carbone pour imprimer le mouvement alternatif au ou à chaque diaphragme ou cylindre dans la chambre.

Drawing